Identification of Quantitative Trait Loci for Plant Height, Crown Diameter, and Plant Biomass in a Pseudo-F 2 Population of Switchgrass

Switchgrass ( Panicum virgatum ) is a perennial warm-season grass that produces high biomass yield. Identification of mechanisms for genetic regulation of biomass traits has potential to facilitate genetic manipulation of switchgrass for enhancing biomass yield. The objective of this study was to identify quantitative trait loci for biomass-related traits in a pseudo-F 2 population of switchgrass derived from an upland cross with a lowland switchgrass cultivar. Plant height (HT), crown diameter (CD), and plant biomass (PB) were assessed in field studies in 2015 and 2016. Plant height was positively correlated with PB in both years but only correlated with CD in 2016. Positive correlations between CD and PB were found in both years. Six quantitative trait loci (QTLs) were detected, including three QTLs on chromosome 2b for HT (2015) or CD (2016), two 2 QTLs on chromosome 2a for CD and PB in 2016, and one QTL on chromosome 5b for CD in 2016. The logarithm of the odds scores for these QTLs ranged from 4.9 to 8.2, and percentage variance explained ranged from 7.1 to 12.9%. One QTL on chromosome 2b appeared to simultaneously control HT in 2015 and CD in 2016. Homologs of candidate genes related to cell wall development and biosynthesis, hormone regulation, and metabolism were identified within the confidence interval of these QTLs. The findings from this study indicate that these QTLs can be important signals for genetic control of switchgrass growth.